The present invention relates to an artificial illuminator for supplying light necessary to cultivate a plant, and, more specifically, to an illuminator which employs a discharge lamp as a light source, thereby enhancing the efficiency of the illuminator.
A method has been proposed which entails supplying the light necessary to breed a plant by irradiating artificial illumination or solar light and supplementing it in a controlled cultivating facility, mainly for agricultural purposes.
An apparatus has been disclosed in Japanese Unexamined Patent Publication No. 55-29991 for suitably illuminating plants by bright and dark rhythms corresponding to day and night which is based on the breeding mechanism of plants. This apparatus is adapted to pass a breeding plant through a position of high illumination directly under ceiling lamps and through a position of low illumination at the intermediate of the lamps in periods substantially corresponding to day and night.
The apparatus is based on the principle that a photosynthesis is accelerated in high illumination corresponding to daytime and a commutation of a photosynthesis product is performed at a low illumination time, as described above.
In the conventional apparatus, costs represent a large portion of plant breeding expense.
The photosynthesis of a plant is generally carried out by a photochemical reaction and a thermochemical reaction. The photochemical reaction necessitates light, but the thermochemical reaction does not require light. Photochemical reaction has a response time of several tens of microseconds and thermochemical reaction has a response time of several tens of milliseconds longer than the photochemical reaction. These reactions are entirely different from the bright and dark rhythm corresponding to day and night.
Further, an apparatus for exciting discharge lamps in high frequency with a "periodic extinquishing" term has been disclosed in Japanese Unexamined Patent Publication No. 47-21979. However, this apparatus merely dims discharge lamps.